Contact image sensor (CIS) scanners are popular computer peripheral devices. They are used for scanning documents or pictures. The conversion results are stored in a digital format or further processed by computers.
The CIS module usually includes a light source, a lens for focusing, an image sensor and a carriage. Since the focal distance of the CIS module is merely 0.3 mm, only documents or pictures within this distance will be clearly scanned. Once the object is outside that range, the scanned image will be blurred. Please refer to FIG. 1. Because of the strict limit, the image sensor 104 may not be able to retrieve clear images if there is a vertical movement brought about by the unevenness of guiding shaft 200 or other mechanical reasons when the carriage 108 moves along the guiding shaft 200. In order to solve this problem, it is known in the conventional techniques that an elastic element 202 is disposed between the carriage 108 and the image sensor 104 to absorb any forces that cause undesirable movement.
However, the limited space between the carriage 108 and the image sensor 104 restricts the size and the elasticity of the elastic element 202, which in turn limit the lifetime of the CIS scanner.